The present disclosure generally relates to semiconductor memory devices and, more particularly, the present disclosure relates to nonvolatile memory devices and to methods for fabricating nonvolatile memory devices.
A claim of priority under 35 U.S.C. § 119 is made to Korean Patent Application No. 2006-97331, filed Oct. 2, 2006, the entire contents of which are hereby incorporated by reference.
In general, semiconductor memory devices are classified into volatile memory devices and nonvolatile memory devices. Volatile memory devices include, for example, a dynamic random access memory (DRAM.) Volatile memory devices have several distinguishing characteristics. For example, the volatile memory devices cannot retain data when power supply is interrupted. On the other hand, the nonvolatile memory devices can retain written data even if power supply is interrupted. Nonvolatile memory devices include, for example, a flash memory device capable of electrically programming and erasing data.
Due to an increase in demand for faster operating but smaller size flash memory, the integration density of flash memory is continually being increased. Furthermore, when a flash memory device is highly integrated, it may be desirable to ensure a predetermined thicknesses of a tunnel dielectric layer and a blocking oxide layer. The predetermined thickness of these layers may help avoid problems associated with cell operation and reliability. In order to ensure a proper thickness of these layers, the integration density of a flash memory device is increased by scaling down the flash memory device planarly rather than vertically.
As the flash memory device is being scaled down, a density of plasma used in a dry etching process for gate patterning is continuously increased. This increase in the plasma density may cause the concentration of an electric field over a small area of the tunnel oxide layer. This phenomenon may damage the tunnel oxide layer. This plasma damage of the tunnel oxide layer may lead to various problems such as, for example, a reduction in the reliability of memory cells, a reduction in the data retained within memory cells, etc.
Thus, there is a need for methods and systems to fabricate high integration density flash memory devices without the undesirable effects associated with an increase in plasma density and the like. The present disclosure is directed towards overcoming the limitations associated with conventional flash memory fabrication methods and systems.